Spontaneous magnetization and resistivity jumps in bilayered manganite (La_0.8Eu_0.2)_4/3Sr_5/3Mn₂O₇ single crystals

Owing to the inhomogeneous state resulting from the doping of a small number of Eu ions into La_4 / 3Sr_5 / 3Mn_2O_7, from the resulting single crystal (La_0.8Eu_0.2)_4 / 3Sr_5 / 3Mn_2O_7 we have observed the magnetization jump, the resistivity jump, as well as the relaxation phenomena. For (La_0.8Eu_0.2)_4 / 3Sr_5 / 3Mn_2O_7, it has a very delicate ground state due to the interplays among spin, charge, orbital, lattice degrees of freedom. Consequently, the magnetization state is sensitive to temperature, magnetic field, as well as time. Meanwhile, the evolution of the magnetization with time shows a spontaneous jump when both the temperature and the magnetic field are constant. Similar step-like behaviours are also observed in resistivity. All these results suggest that Eu doping can greatly modulate the physical properties of La_4 / 3Sr_5 / 3Mn_2O_7 and cause such interesting behaviours.